If you don't recognize him as 35-year-old actor Clifton Collins Jr., you probably know him as homosexual assassin Francisco Flores, soldier-in-training Private Miter, or paranoid drug dealer Rupert Guest. Collins represents a rare breed of Hollywood player whose personality completely vanishes on screen, leaving only nuanced characters in films like Traffic (2000), Tigerland (2000), and The Rules Of Attraction (2002). Since he began acting professionally at age 17, the grandson of pioneering Mexican-American actor Pedro Gonzales-Gonzales has brought depth to over 30 varied roles, be they bit parts or major characters. "This is the only job that you get to be anybody," he says. "As an actor you can be a doctor, lawyer, all these different things. I love just learning about different occupations and different environments, different cultures."

Collins locates each character through intense preparation. For his Oscar-worthy turn as real-life convicted murderer Perry Smith in Capote (2005), he pored over In Cold Blood, Truman Capote's 1966 account of Smith's crimes, trial, and execution. He listened to songs that Smith once sang and discovered mannerisms in video footage and Richard Avedon photos. "You could see the shame weighing in on his shoulders," says Collins. "He was really uncomfortable in his own skin."

When necessary, Collins visits darker places. In Traffic, his character is tortured for information, so he discussed the practice with Mexican police and doctors, who explained that cayenne pepper shot into the sinus cavity feels like "dumping your head in a vat of french fry oil." Though the disturbing scene is based on the real-life torture of slain DEA agent Enrique Camarena, Collins decided against listening to audiotape of it. "I couldn't validate any reasons for me to listen to a man suffering," he says, adding, "nor could I ever aspire to bring that kind of pain to this scene." You do feel his pain, though, and the pleasure is all yours.